fix: use correct variable for repository delete (github#26139)

Author: mikesurowiec

.github/workflows/azure-preview-env-destroy.yml

@@ -61,7 +61,7 @@ jobs:
       # This will fail if the IMAGE_REPO doesn't exist, but we don't care
       - name: 'Untag all docker images for this PR'
         run: |
-          az acr repository delete -n ${{ secrets.NONPROD_REGISTRY_NAME }} --repository ${{ env.IMAGE_REPO }} -y || true
+          az acr repository delete -n ${{ secrets.NONPROD_REGISTRY_SERVER }} --repository ${{ env.IMAGE_REPO }} -y || true
 
       # Remove all GitHub deployments from this environment and remove the environment
       - uses: strumwolf/delete-deployment-environment@45c821e46baa405e25410700fe2e9643929706a0